The present invention relates to an engine in which a sprocket is fixed to one end of a camshaft supported in a camshaft support member and a timing chain is wrapped around the sprocket and, in particular, to a timing chain lubricating structure therefor.
A camshaft of an overhead camshaft type engine is driven by an arrangement in which a sprocket fixed to a shaft end of the camshaft is linked to a sprocket fixed to a shaft end of a crankshaft via a timing chain. A lubricating structure for such a timing chain is known in Japanese Patent Application Laid-open No. 6-146838. The timing chain lubricating structure disclosed in the above-mentioned application has an arrangement in which a relief valve is provided in an oil passage for supplying oil to a hydraulic tappet, and the section where the sprocket is meshed with the chain is lubricated with a jet of oil that issues from an oil jet that is integral with the relief valve.
In the above-mentioned conventional arrangement, because the oil jet is placed in a small space surrounded by an intake camshaft sprocket, an exhaust camshaft sprocket and a timing chain wrapped around the two sprockets, securing a space for mounting the oil jet not only prevents a reduction in the dimensions of the engine but also raises a possibility that the degree of freedom when positioning another member such as a chain guide might be reduced.
The present invention has been carried out in view of the above-mentioned circumstances, and it is an object of the present invention to compactly arrange an oil jet that issues a jet of oil for lubricating a timing chain.
In order to achieve the above-mentioned object, in accordance with a first aspect of the present invention, there is proposed a timing chain lubricating structure for an engine in which a sprocket is fixed to an end of a camshaft supported in a camshaft support member and a timing chain is wrapped around the sprocket, comprising an oil jet that issues a jet of oil for lubricating.the timing chain, the oil jet being placed between the sprocket and the camshaft support member.
In accordance with the above-mentioned arrangement, because the oil jet is placed by effectively using the space defined between the sprocket and the camshaft support member, it is possible to minimize the increase in the dimensions of the engine and interference with the mounting of another member due to the mounting of the oil jet.
Furthermore, in accordance with a second aspect of the present invention, in addition to the above-mentioned first aspect, there is proposed a timing chain lubricating structure for an engine wherein the oil jet is placed so as to face a cut-out hole formed in the sprocket.
In accordance with the above-mentioned arrangement, because the oil jet is placed so as to face the cut-out hole of the sprocket, the state in which the oil jet is mounted can be easily checked through the cut-out hole of the sprocket.
Furthermore, in accordance with a third aspect of the present invention, there is proposed a timing chain lubricating structure for an engine in which sprockets are fixed to ends of a pair of camshafts supported in a camshaft support member and a timing chain is wrapped around these sprockets, comprising a variable cam phase mechanism provided on one of the pair of sprockets and an oil jet that issues a jet of oil for lubricating the timing chain, the oil jet being placed between the other sprocket and the camshaft support member.
In accordance with the above-mentioned arrangement, because the variable cam phase mechanism is provided on one sprocket and the oil jet is placed by effectively using the space defined between the camshaft support member and the other sprocket, which has no variable cam phase mechanism, it is possible to minimize the increase in the dimensions of the engine and interference with the mounting of another member due to the mounting of the oil jet.
Furthermore, in accordance with a fourth aspect of the present invention, in addition to the above-mentioned third aspect, there is proposed a timing chain lubricating structure for an engine wherein the oil jet is placed so as to face a cut-out hole formed in the other sprocket.
In accordance with the above-mentioned arrangement, because the oil jet is placed so as to face the cut-out hole formed in the other sprocket, the state in which the oil jet is mounted can be easily checked through the cut-out hole of the sprocket.
Furthermore, in accordance with a fifth aspect or a seventeenth aspect of the present invention, in addition to the above-mentioned first aspect or third aspect, there.is proposed a timing chain lubricating structure for an engine wherein the oil jet is supported in the camshaft support member, the oil jet and at least one bolt among a plurality of bolts fastening the camshaft support member overlap one another in the camshaft direction, and the above-mentioned at least one bolt is offset toward the side away from the sprocket relative to any of the remaining bolts.
In accordance with the above-mentioned arrangement, because the oil jet supported in the camshaft support member and at least one bolt among the plurality of bolts fastening the camshaft support member overlap one another in the camshaft direction, it is unnecessary to increase the dimensions of the camshaft support member in order to mount the oil jet and, moreover, the rigidity with which the camshaft is supported can be enhanced by avoiding forming a mounting hole for the oil jet in a position close to the plane in which the camshaft is supported. Furthermore, because the above-mentioned at least one bolt is offset toward the side away from the sprocket relative to any of the remaining bolts, a space for mounting the oil jet can be secured and the support rigidity can be enhanced.
Furthermore, in accordance with a sixth aspect or an eighteenth aspect of the present invention, in addition to the above-mentioned first aspect or third aspect, there is proposed a timing chain lubricating structure for an engine, wherein the oil jet is supported in the camshaft support member, the oil jet and at least one bolt among a plurality of bolts fastening the camshaft support member overlap one another in the camshaft direction, and the timing chain lubricating structure further comprises an oil passage extending to the oil jet and formed on the outer periphery of the above-mentioned at least one bolt.
In accordance with the above-mentioned arrangement, because the oil jet supported in the camshaft support member and at least one bolt among the plurality of bolts fastening the camshaft support member overlap one another in the camshaft direction, it is unnecessary to increase the dimensions of the camshaft support member in order to mount the oil jet and, moreover, the rigidity with which the camshaft is supported can be enhanced by avoiding forming a mounting hole for the oil jet in a position close to the plane in which the camshaft is supported. Furthermore, because the oil passage extending to the oil jet is formed on the outer periphery of the above-mentioned at least one bolt, the length of the oil passage can be reduced.
Furthermore, in accordance with a seventh aspect or a thirteenth aspect of the present invention, in addition to the above-mentioned first aspect or third aspect, there is proposed a timing chain lubricating structure for an engine, wherein the oil jet is fastened to the camshaft support member.
In accordance with the above-mentioned arrangement, because the oil jet is fastened to the camshaft support member, it is unnecessary to employ a special member for supporting the oil jet.
Furthermore, in accordance with an eighth aspect or a fourteenth aspect of the present invention, in addition to the above-mentioned third aspect or seventh aspect, there is proposed a timing chain lubricating structure for an engine wherein the camshaft support member comprises an upper camshaft holder and a lower camshaft holder, and the oil jet is fastened to the lower camshaft holder.
In accordance with the above-mentioned arrangement, because the camshaft support member comprises the upper camshaft holder and the lower camshaft holder and the oil jet is fastened to the lower camshaft holder, the rigidity with which the camshaft and the oil jet are supported can be enhanced.
Furthermore, in accordance with a ninth, fifteenth or sixteenth aspect of the present invention, in addition to the above-mentioned fifth, sixth or seventh aspect, there is proposed a timing chain lubricating structure for an engine wherein the axis of a bolt fastening the oil jet to the camshaft support member and the axis of a bolt fastening the camshaft support member to a cylinder head are offset from each other in a direction perpendicular to the camshaft.
In accordance with the above-mentioned arrangement, because the axis of the bolt fastening the oil jet to the camshaft support member and the axis of the bolt fastening the camshaft support member to the cylinder head are offset from each other in the direction perpendicular to the camshaft, the rigidity with which the oil jet is fastened can be maintained while suppressing any increase in the dimension of the camshaft support member in the camshaft direction.
Furthermore, in accordance with a tenth aspect or a twelfth aspect of the present invention, in addition to the above-mentioned seventh or eleventh aspect, there is proposed a timing chain lubricating structure for an engine, further comprising a chain guide that is in contact with the outer surface of the timing chain in a direction in which the oil jet issues a jet of oil.
In accordance with the above-mentioned arrangement, because the chain guide is in contact with the outer surface of the timing chain in the direction in which the oil jet issues a jet of oil, the jet of oil issued from the oil jet can be effectively used.
Furthermore, in accordance with an eleventh aspect of the present invention, in addition to the above-mentioned third aspect, there is proposed a timing chain lubricating structure for an engine, wherein the oil jet issues a jet of oil toward a position immediately before the section where the one sprocket having the variable cam phase mechanism is meshed with the timing chain.
In accordance with the above-mentioned arrangement, because the oil jet issues a jet of oil toward the position immediately before the section where the one sprocket having the variable cam phase mechanism is meshed with the timing chain, it is easy to issue a jet of oil toward the position immediately before the meshed section.
Furthermore, in accordance with a nineteenth or twentieth aspect of the present invention, in addition to the above-mentioned second or fourth aspect, there is proposed a timing chain lubricating structure for an engine, further comprising a bolt for fastening the oil jet, the bolt facing the cut-out hole.
In accordance with the above-mentioned arrangement, since the bolt for fastening the oil jet faces the cut-out hole formed in the sprocket, the bolt can be attached/detached through the cut-out hole thus enhancing the workability.
An intake camshaft 12 and an exhaust camshaft 13 of the embodiments correspond to the camshafts of the present invention, an intake camshaft sprocket 15 of the embodiments corresponds to the one sprocket of the present invention, an exhaust camshaft sprocket 16 of the embodiments corresponds to the other sprocket of the present invention, a lower camshaft holder 25 of the embodiments corresponds to the camshaft support member of the present invention, bolts 27 and 30 of the embodiments correspond to any of the remaining bolts of the present invention, a bolt 28 of the embodiments corresponds to said at least one bolt of the present invention, and a second variable valve operating characteristic mechanism V2 of the embodiments corresponds to the variable cam phase mechanism of the present invention.
The above-mentioned objects, other objects, characteristics and advantages of the present invention will become apparent from explanation of preferred embodiments that will be described in detail below by reference to the attached drawings.